Research on improvement of radioactivity quantitation in the human body in thallium-201 scintigraphic imaging study

在核医学研究中，准确估计放射性在人体内的分布对于利用核素图像进行可靠的诊断是非常重要的。首先，利用蒙特卡罗程序和个人计算机模拟了Tl-201在体模中发射的光子，并详细分析了体模外探测到的光子的能量分布。根据成像窗口中含有真实发射位置信息的未散射光子和含有虚假发射位置信息的散射光子的数量，我们可以提出一种散射校正方法。接下来，我们使用伽马相机对一个简单的体模进行了TL-201平面成像，并对采集的图像应用了这种散射校正方法。结果表明，与传统的散射校正方法相比，这种散射校正方法能够更准确、有效地区分非散射光子和散射光子。此外，为了研究散射校正和衰减校正如何在定量上改善SPECT值，使用双头伽马相机SPECT系统和复杂的体模进行了TL-201心肌SPECT成像。采用了与该项目的联合研究人员共同开发的衰减校正方法。从这项心肌SPECT实验的结果来看，为了提高SPECT在心肌成像中的定量价值，对经过精确散射校正的SPECT图像进行衰减校正变得非常重要。我们认为，我们的研究结果可能对临床上提供更准确的诊断信息的TL-201心肌成像非常有用。

In the nuclear medicine study, it is very important to accurately estimate radioactivity distribution in the human body for reliable diagnosis with scintigraphic images. In this study, we investigated it about improvement of radioactivity quantitation in the human body in thallium-201 (Tl-201) scintigraphic imaging.First, we simulated the photons emitted from Tl-201 in a phantom using Monte Carlo programs and a personal computer, and analyzed energy distributions for photons detected outside the phantom in detail. From the amount of non-scattered with true emission location information and scattered photons with false emission location information contained within the imaging window, we could develop a scatter correction method. Next, we performed Tl-201 planar imaging of a simple phantom using a gamma camera and applied this scatter correction method for the images acquired. The results showed that this scatter correction method can distinguish non-scattered photons from scattered photons more accurately and effectively in comparison with the conventional ones. In addition, to investigate how both scatter arid attenuation corrections can quantitatively improve SPECT values, Tl-201 myocardial SPECT imaging was performed using a dual-head gamma camera SPECT system and a sophisticated phantom. The attenuation correction method which was developed with the joint researchers in this project was employed. From the results of this myocardial SPECT experiments, in order to improve quantitative SPECT value in the myocardial imaging, it became clear to be important to apply the attenuation correction to accurately scatter-corrected SPECT images.We consider that our results from this research may be very useful to clinical Tl-201 myocardial imaging with more accurate diagnostic information.